Investigation of the antibacterial defense mechanisms of the lower urinary tract will be continued over the next year in the following two phases: 1. Investigation of vaginal, perineal, and rectal flora in normal and cystitis-prone student nurses and urologic patients. The student nurses at a large teaching hospital will be divided into two groups -- those with history of cystitis and those without -- by means of an extensive questionnaire, which will also be given to urologic patients. Periodically, a midstream urine culture will be performed, and cultures will also be taken from the vagina, perineum. The vaginal secretions will be investigated for bactericidal and bacteriostatic activity. The migration of pathogenic bacteria from the rectum to the vagina and then to the bladder will be demonstrated in cystitis-prone women. Hopefully, clues as to the etiology of this auto-infection will be found so that treatment can be improved. 2. Investigation of bladder antibacterial defense mechanisms. Varying numbers of gram-negative pathogens will be introduced into the New Zealand White male rabbit's bladder by direct needle puncture. Studies utilizing this mode., which has been developed over the past year, will include: a) The effects of pH, divalent cations, NaF, NaCl, and trauma on the kinetics of bacterial-vesical mucosa interaction; b) Isolation of the substance or substances responsible for the lack of bacterial absorption onto the vesical mucosa; c) Electron microscopic and autoradiographic studies of bacteria-bladder cell interaction in the normal and insulted bladder.